/** An instance of this class can calculate, via its sqrt() methods, an
**  approximation to the square root of a given number of type either
**  long or int.
**  @author R. McCloskey
**  @version Feb. 2005
*/

public class SquareRootCalc {


   /** Calculates the floor of the square root of k.
   **  @param k the value whose square root is to be computed.
   **  @pre: 0 <= k
   **  @return r satisfying r<sup>2</sup> &le; k &lt; (r+1)<sup>2</sup>
   **  @throws IllegalArgumentException in case the precondition is not met
   */
   public long sqrt(long k) {

      if (k < 0) {
         throw new IllegalArgumentException("sqrt() requires nonnegative arg");
      }

      // use binary search to calculate square root of k
      long low = 0, high = k+1, mid;

      // loop invariant: low^2 <= k < high^2
      while (low != high-1) {
         mid = (low + high) / 2;   // assertion low < mid < high
         if (mid * mid <= k)
            { low = mid; }
         else // mid * mid > k
            { high = mid; }
      }
      return low;
   }


   /** Calculates the floor of the square root of k.
   **  @param k the value whose square root is to be computed.
   **  @pre: 0 &lt;= k
   **  @return r satisfying r<sup>2</sup> &lt;= k &lt; (r+1)<sup>2</sup>
   */
   public int sqrt(int k) {
      return (int) sqrt((long) k);
   }


}